feat(db-bench): prove batches form — the write-concurrent leg, T4
databasev2 4 part A, task 4. Scope extended with developer approval: the plan authorised touching the sample only for observability, but no existing leg has enough concurrent durable writes to exercise group commit at all, so the payoff was unevaluable either way. The finding that forced it: - `mix` writes on one op in ten with C=4 (all_mode calls mix_mode(n/10, 4); Mixer writes on i % 10 == 9), so the quick run performs 20 writes total. Measured mean batch 1.01 over 3112 barriers, peak 3 - that is a property of the WORKLOAD, not the mechanism: peak 3 of a possible 4 shows batches form whenever writes actually coincide - `wmix N C` added: every op a durable write, C at once. Updates rather than inserts, so it is comparable to mixwrite and the row count stays flat. Histogram kind 2 — a replayed store still holds the seeding run's kind-0/1 Hist rows and merging those would report someone else's latencies - WO_WAL_STATS=1 prints one line at exit: batches, records, peak_batch, peak_staged. Opt-in, because it would otherwise pollute every durable program's output. Counters live in wo_wal; no builtin, the numbers are diagnostic and not part of the language Measured, and it scales with concurrency exactly as designed: - C = 4 / 16 / 64 -> mean batch 1.13 / 1.76 / 5.35, peak 3 / 10 / 39 - the gate's own legs: durable.s1 5412 records over 5412 barriers (mean 1.0, peak 1 — the inline path, one barrier per statement BY DESIGN), durable.sN 7757 over 2296 (mean 3.38, peak 28) at 2x the throughput - peak staged 1372 B settles the no-cap decision with a number: the batch is tiny, so the upstream mailbox bound is sufficient - mean_batch/peak_batch are higher-is-better (the default detector would have called bigger batches worse) - only the batch SHAPE metrics are waived to 100%; wmix throughput and latency keep real tolerances (15% s1, 50% sN) — a blanket waiver would have left the entire new leg ungated - the live assertion `mean > 1.0` on the sN leg is what catches inertness - gate bites: sN wmix ops_sec -60% -> FAIL on exactly that metric, 1 of 86 Verified: db-bench-quick 89 checks 0 failures; baseline refreshed (86 metrics). Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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"tolerance_pct": 50,
|
||||
"value": 64
|
||||
"value": 72
|
||||
},
|
||||
"ram.sN.mixwrite.p99us": {
|
||||
"dir": "lower",
|
||||
"floor": 516,
|
||||
"floor": 344,
|
||||
"tolerance_pct": 50,
|
||||
"value": 129
|
||||
"value": 86
|
||||
},
|
||||
"ram.sN.msgrate.msgs_sec": {
|
||||
"dir": "higher",
|
||||
"floor": 355876,
|
||||
"floor": 176056,
|
||||
"tolerance_pct": 50,
|
||||
"value": 2847015
|
||||
"value": 1408450
|
||||
},
|
||||
"ram.sN.query.ops_sec": {
|
||||
"dir": "higher",
|
||||
"floor": 307125,
|
||||
"floor": 308641,
|
||||
"tolerance_pct": 50,
|
||||
"value": 1228501
|
||||
"value": 1234567
|
||||
},
|
||||
"ram.sN.query.p50us": {
|
||||
"dir": "lower",
|
||||
|
|
@ -398,9 +470,9 @@
|
|||
},
|
||||
"ram.sN.read.ops_sec": {
|
||||
"dir": "higher",
|
||||
"floor": 340692,
|
||||
"floor": 310945,
|
||||
"tolerance_pct": 50,
|
||||
"value": 1362769
|
||||
"value": 1243781
|
||||
},
|
||||
"ram.sN.read.p50us": {
|
||||
"dir": "lower",
|
||||
|
|
@ -416,38 +488,38 @@
|
|||
},
|
||||
"ram.sN.seed.ops_sec": {
|
||||
"dir": "higher",
|
||||
"floor": 72890,
|
||||
"floor": 363372,
|
||||
"tolerance_pct": 50,
|
||||
"value": 291562
|
||||
"value": 1453488
|
||||
},
|
||||
"ram.sN.seed.p50us": {
|
||||
"dir": "lower",
|
||||
"floor": 100,
|
||||
"tolerance_pct": 50,
|
||||
"value": 3
|
||||
"value": 1
|
||||
},
|
||||
"ram.sN.seed.p99us": {
|
||||
"dir": "lower",
|
||||
"floor": 100,
|
||||
"tolerance_pct": 50,
|
||||
"value": 7
|
||||
"value": 2
|
||||
},
|
||||
"ram.sN.write.ops_sec": {
|
||||
"dir": "higher",
|
||||
"floor": 60518,
|
||||
"floor": 202922,
|
||||
"tolerance_pct": 50,
|
||||
"value": 242072
|
||||
"value": 811688
|
||||
},
|
||||
"ram.sN.write.p50us": {
|
||||
"dir": "lower",
|
||||
"floor": 100,
|
||||
"tolerance_pct": 50,
|
||||
"value": 6
|
||||
"value": 1
|
||||
},
|
||||
"ram.sN.write.p99us": {
|
||||
"dir": "lower",
|
||||
"floor": 100,
|
||||
"tolerance_pct": 50,
|
||||
"value": 9
|
||||
"value": 4
|
||||
}
|
||||
}
|
||||
|
|
@ -393,7 +393,8 @@ int wo_wal_append_remove(wo_wal *w, uint32_t class_id, uint64_t id) {
|
|||
}
|
||||
|
||||
int wo_wal_commit(wo_wal *w) {
|
||||
if (!w->len) return 0;
|
||||
if (!w->len) return 0; /* empty commits are not batches; do not count them */
|
||||
if (w->len > w->stat_peak_staged) w->stat_peak_staged = w->len;
|
||||
size_t at = 0;
|
||||
while (at < w->len) {
|
||||
ssize_t n = pwrite(w->fd, w->buf + at, w->len - at, (off_t)(w->off + at));
|
||||
|
|
@ -425,8 +426,16 @@ static void wal_die(const wo_wal *w, const char *op, uint32_t nrec) {
|
|||
void wo_wal_stage_fatal(const wo_wal *w) { wal_die(w, "staging a record", 1); }
|
||||
|
||||
void wo_wal_commit_fatal(wo_wal *w, uint32_t nrec) {
|
||||
int staged = w->len != 0;
|
||||
int rc = wo_wal_commit(w);
|
||||
if (rc == 0) return;
|
||||
if (rc == 0) {
|
||||
if (staged) { /* count the barrier that actually happened */
|
||||
w->stat_batches++;
|
||||
w->stat_records += nrec;
|
||||
if (nrec > w->stat_peak_batch) w->stat_peak_batch = nrec;
|
||||
}
|
||||
return;
|
||||
}
|
||||
wal_die(w, rc == WO_WAL_ERR_SYNC ? "fdatasync" : "pwrite", nrec);
|
||||
}
|
||||
|
||||
|
|
|
|||
|
|
@ -55,6 +55,15 @@ typedef struct wo_wal {
|
|||
/* staged batch: appended by wal_append_*, flushed by wal_commit */
|
||||
uint8_t *buf;
|
||||
size_t len, cap;
|
||||
/* databasev2 4: group-commit diagnostics. Batching is worthless if
|
||||
* batches are always one, and a throughput change would then have come
|
||||
* from somewhere else — so the mechanism is measured, not assumed.
|
||||
* peak_staged also settles whether the batch needs a cap with a number
|
||||
* instead of a guess. Reported at exit under WO_WAL_STATS. */
|
||||
uint64_t stat_batches; /* non-empty commits */
|
||||
uint64_t stat_records; /* records those commits carried */
|
||||
uint64_t stat_peak_batch; /* most records in one barrier */
|
||||
uint64_t stat_peak_staged; /* most bytes staged behind one barrier */
|
||||
} wo_wal;
|
||||
|
||||
/* Open (create if missing) and preallocate [prealloc] bytes (best-effort;
|
||||
|
|
|
|||
|
|
@ -337,6 +337,91 @@ class Mixer {
|
|||
}
|
||||
}
|
||||
|
||||
-- databasev2 4 part A: every op a durable write, C at once.
|
||||
--
|
||||
-- Why this leg exists. `mix` writes on one op in ten with C=4, so at most a
|
||||
-- handful of writes are ever in flight and group commit has almost nothing to
|
||||
-- batch: measured mean batch 1.01 over 3112 barriers, peak 3. That is a
|
||||
-- property of the WORKLOAD, not of the mechanism, and without a write-
|
||||
-- concurrent leg the iteration's payoff cannot be evaluated either way.
|
||||
--
|
||||
-- Updates rather than inserts: comparable to what `mixwrite` measures, and the
|
||||
-- row count stays flat so a long run does not turn into a growth test.
|
||||
-- Histogram kind 2, because a replayed store still holds the seeding run's
|
||||
-- kind-0/1 Hist rows and merging those would report someone else's latencies.
|
||||
class WJob {
|
||||
ops: Int
|
||||
seed: Int
|
||||
kmod: Int
|
||||
}
|
||||
|
||||
class WMixer {
|
||||
id: Int
|
||||
fn receive(msg: WJob) {
|
||||
let hw: map<Int, Int> = {};
|
||||
let s = msg.seed;
|
||||
let i = 0;
|
||||
while i < msg.ops {
|
||||
s = lcg(s);
|
||||
let key = s % msg.kmod;
|
||||
let o0 = time.ticks();
|
||||
for r in from x in Item where x.k == key take 1 select x {
|
||||
r.v = r.v + 1;
|
||||
}
|
||||
hist_add(hw, time.ticks() - o0);
|
||||
i = i + 1;
|
||||
}
|
||||
hist_dump(hw, 2);
|
||||
insert Meta { tag: "wmixdone${self.id}", val: msg.ops };
|
||||
}
|
||||
}
|
||||
|
||||
fn wmix_mode(total: Int, c: Int) -> Int {
|
||||
let kmod = meta_val("kmod");
|
||||
if kmod < 1 {
|
||||
print_err("wmix: seed first");
|
||||
return 1;
|
||||
}
|
||||
let per = total / c;
|
||||
if per < 1 {
|
||||
per = 1;
|
||||
}
|
||||
let wall0 = time.ticks();
|
||||
let i = 0;
|
||||
while i < c {
|
||||
let a: actor WJob = spawn WMixer { id: i };
|
||||
send(a, WJob { ops: per, seed: 4242 + i * 7919, kmod: kmod });
|
||||
i = i + 1;
|
||||
}
|
||||
let done = 0;
|
||||
while done < c {
|
||||
time.sleep(20);
|
||||
done = 0;
|
||||
i = 0;
|
||||
while i < c {
|
||||
if meta_val("wmixdone${i}") >= 0 {
|
||||
done = done + 1;
|
||||
}
|
||||
i = i + 1;
|
||||
}
|
||||
}
|
||||
let wall = time.ticks() - wall0;
|
||||
let hw: map<Int, Int> = {};
|
||||
let nw = 0;
|
||||
for x in from x in Hist select x {
|
||||
if x.kind == 2 {
|
||||
if has(hw, x.b) {
|
||||
set(hw, x.b, get(hw, x.b) + x.c);
|
||||
} else {
|
||||
set(hw, x.b, x.c);
|
||||
}
|
||||
nw = nw + x.c;
|
||||
}
|
||||
}
|
||||
report("wmix", nw, wall, hw);
|
||||
return 0;
|
||||
}
|
||||
|
||||
fn mix_mode(total: Int, c: Int) -> Int {
|
||||
let kmod = meta_val("kmod");
|
||||
if kmod < 1 {
|
||||
|
|
@ -465,7 +550,7 @@ fn all_mode(n: Int) -> Int {
|
|||
fn usage() -> Int {
|
||||
print_err("usage: db-bench <mode>");
|
||||
print_err(" all N | seed N | read N | query N | write N | wal N");
|
||||
print_err(" mix N C | msgrate N | verify | verify-acked M");
|
||||
print_err(" mix N C | wmix N C | msgrate N | verify | verify-acked M");
|
||||
return 2;
|
||||
}
|
||||
|
||||
|
|
@ -508,6 +593,17 @@ fn main(args: multi Text) -> Int {
|
|||
if args[0] == "msgrate" {
|
||||
return msgrate_mode(n);
|
||||
}
|
||||
if args[0] == "wmix" {
|
||||
if len(args) < 3 {
|
||||
return usage();
|
||||
}
|
||||
let wc = parse_int(args[2]);
|
||||
if wc == nil or wc < 1 {
|
||||
print_err("db-bench: <c> must be a positive number");
|
||||
return 2;
|
||||
}
|
||||
return wmix_mode(n, wc);
|
||||
}
|
||||
if args[0] == "mix" {
|
||||
if len(args) < 3 {
|
||||
return usage();
|
||||
|
|
|
|||
|
|
@ -125,6 +125,16 @@ static void gc_pump(wo_vm *vm) {
|
|||
}
|
||||
}
|
||||
|
||||
/* databasev2 4: one diagnostic line about group commit, opt-in via
|
||||
* WO_WAL_STATS. Off by default because it would otherwise pollute the output
|
||||
* of every durable program; a gate that wants the numbers asks for them. */
|
||||
static void wal_stats_report(const wo_wal *w) {
|
||||
if (!w || !getenv("WO_WAL_STATS")) return;
|
||||
fprintf(stderr, "walstats batches=%llu records=%llu peak_batch=%llu peak_staged=%llu\n",
|
||||
(unsigned long long)w->stat_batches, (unsigned long long)w->stat_records,
|
||||
(unsigned long long)w->stat_peak_batch, (unsigned long long)w->stat_peak_staged);
|
||||
}
|
||||
|
||||
int main(int argc, char **argv) {
|
||||
wo_module mod;
|
||||
char err[256];
|
||||
|
|
@ -245,7 +255,7 @@ int main(int argc, char **argv) {
|
|||
if (wo_engine_start(&mod, heap_mb << 20, nshards) != 0) {
|
||||
fprintf(stderr, "wovm: cannot start %u shards\n", nshards);
|
||||
wo_engine_stop();
|
||||
if (VM.rt.wal) wo_wal_close(&WAL);
|
||||
if (VM.rt.wal) { wal_stats_report(&WAL); wo_wal_close(&WAL); }
|
||||
wo_db_destroy(&DB);
|
||||
wo_vm_destroy(&VM);
|
||||
wo_module_free(&mod);
|
||||
|
|
@ -304,7 +314,7 @@ int main(int argc, char **argv) {
|
|||
* unwind. */
|
||||
if (argv_val) wo_drop_kind(&VM.rt, WO_K_MULTI, argv_val);
|
||||
wo_engine_stop(); /* join + destroy the worker shards before the primary */
|
||||
if (VM.rt.wal) wo_wal_close(&WAL);
|
||||
if (VM.rt.wal) { wal_stats_report(&WAL); wo_wal_close(&WAL); }
|
||||
wo_db_destroy(&DB);
|
||||
gc_pump(&VM);
|
||||
wo_vm_destroy(&VM);
|
||||
|
|
|
|||
|
|
@ -26,6 +26,13 @@ QUICK = "--quick" in sys.argv
|
|||
WRITE_BASELINE = "--write-baseline" in sys.argv
|
||||
|
||||
N = 2000 if QUICK else 20000
|
||||
# databasev2 4: the write-concurrent leg. `mix` writes on one op in ten with
|
||||
# C=4, so group commit had almost nothing to batch there (measured mean batch
|
||||
# 1.01, peak 3) — a property of that workload, not of the mechanism. C is high
|
||||
# on purpose: batching is a function of how many writes are in flight, and
|
||||
# measured mean batch rose 1.13 -> 1.76 -> 5.35 at C = 4 -> 16 -> 64.
|
||||
WMIX_N = 4000 if QUICK else 20000
|
||||
WMIX_C = 32 if QUICK else 64
|
||||
MSG_N = 20000 if QUICK else 200000
|
||||
WAL_N = 800 if QUICK else 4000
|
||||
CRASH_REPS = 1 if QUICK else 3
|
||||
|
|
@ -95,6 +102,55 @@ def parse_metrics(lines, into, prefix):
|
|||
if m:
|
||||
into[f"{prefix}.msgrate.msgs_sec"] = int(m.group(2))
|
||||
|
||||
def wmix_leg(metrics, tag, env, data):
|
||||
"""Every op a durable write, WMIX_C at once — the leg that actually
|
||||
exercises group commit.
|
||||
|
||||
It reuses the store the `all` run just seeded (a fresh process replays it,
|
||||
so `kmod` is there) and asks the runtime for its group-commit counters via
|
||||
WO_WAL_STATS. The counters matter as much as the throughput: if batches are
|
||||
always one the mechanism is inert and any throughput change came from
|
||||
somewhere else, so a payoff would be attributed to the wrong cause."""
|
||||
e = dict(env); e["WO_WAL_STATS"] = "1"
|
||||
rc, lines, _, _ = run(["wmix", str(WMIX_N), str(WMIX_C)], e, 1800)
|
||||
if rc != 0:
|
||||
bad(f"{tag}.wmix", f"rc={rc} tail={lines[-2:]}")
|
||||
return
|
||||
ops = p50 = p99 = None
|
||||
batches = records = peak_batch = peak_staged = None
|
||||
for l in lines:
|
||||
f = l.split()
|
||||
if f and f[0] == "wmix" and len(f) == 5:
|
||||
ops, p50, p99 = int(f[2]), int(f[3]), int(f[4])
|
||||
elif f and f[0] == "walstats":
|
||||
kv = dict(x.split("=", 1) for x in f[1:] if "=" in x)
|
||||
batches = int(kv.get("batches", 0)); records = int(kv.get("records", 0))
|
||||
peak_batch = int(kv.get("peak_batch", 0)); peak_staged = int(kv.get("peak_staged", 0))
|
||||
if ops is None or batches is None:
|
||||
bad(f"{tag}.wmix", "no report or no walstats line")
|
||||
return
|
||||
metrics[f"{tag}.wmix.ops_sec"] = ops
|
||||
metrics[f"{tag}.wmix.p50us"] = p50
|
||||
metrics[f"{tag}.wmix.p99us"] = p99
|
||||
metrics[f"{tag}.wmix.peak_batch"] = peak_batch
|
||||
metrics[f"{tag}.wmix.peak_staged"] = peak_staged
|
||||
mean = round(records / batches, 2) if batches else 0
|
||||
metrics[f"{tag}.wmix.mean_batch"] = mean
|
||||
ok(f"{tag}.wmix: {ops} ops/sec, p50 {p50}us p99 {p99}us; "
|
||||
f"{records} records over {batches} barriers (mean {mean}, peak {peak_batch}), "
|
||||
f"peak staged {peak_staged}B")
|
||||
# The gate that matters. Only the MULTI-shard leg can batch: a worker's
|
||||
# statements marshal to shard 0 and queue, while shard-0 statements run
|
||||
# inline and commit one at a time by design (see db.c).
|
||||
if tag.endswith(".sN"):
|
||||
if mean > 1.0:
|
||||
ok(f"{tag}.wmix batches form (mean {mean} > 1)")
|
||||
else:
|
||||
bad(f"{tag}.wmix-inert",
|
||||
f"mean batch {mean} — group commit is not engaging, so a "
|
||||
f"throughput change would not be attributable to it")
|
||||
|
||||
|
||||
def campaign():
|
||||
metrics = {}
|
||||
ncores = os.cpu_count() or 1
|
||||
|
|
@ -123,6 +179,8 @@ def campaign():
|
|||
bad(f"{tag}.mix.fds", f"grew {fdg}")
|
||||
else:
|
||||
ok(f"{tag}.mix.fds flat")
|
||||
if flavor == "durable" and data:
|
||||
wmix_leg(metrics, tag, env, data)
|
||||
if data: shutil.rmtree(data, ignore_errors=True)
|
||||
# msgrate once per shard count, RAM only (no store dependency)
|
||||
for shards in (1, ncores):
|
||||
|
|
@ -225,6 +283,13 @@ def tolerance_for(key):
|
|||
mix*: scheduling-dependent small counts. read/query + all .sN.*:
|
||||
machine jitter, and at post-index-µs scale a 1µs histogram step on a
|
||||
7µs p50 is already 14%."""
|
||||
# databasev2 4: batch SHAPE follows arrival timing, so gating it tightly
|
||||
# would gate the scheduler — what must hold is that the mean exceeds one
|
||||
# under contention, which wmix_leg asserts directly against the live run.
|
||||
# wmix's throughput and latency are NOT waived: they are the payoff, and a
|
||||
# blanket waiver here would have left the whole leg ungated.
|
||||
if key.endswith((".wmix.mean_batch", ".wmix.peak_batch", ".wmix.peak_staged")):
|
||||
return 100
|
||||
if ".mixread." in key or ".mixwrite." in key: return 50
|
||||
if ".sN." in key: return 50
|
||||
if ".read." in key or ".query." in key: return 50
|
||||
|
|
@ -236,7 +301,7 @@ def write_baseline(metrics):
|
|||
"tolerances come from tolerance_for() in the driver"}}
|
||||
for k, v in sorted(metrics.items()):
|
||||
if k.endswith(("rss_growth_kb", "fd_growth")): continue
|
||||
higher = k.endswith(("ops_sec", "msgs_sec"))
|
||||
higher = k.endswith(("ops_sec", "msgs_sec", "mean_batch", "peak_batch"))
|
||||
floor_div = 8 if k.endswith("msgs_sec") else 4
|
||||
# latency floors never sit below 100µs: at post-index µs scale a
|
||||
# 4×1µs "catastrophe line" is noise; the tripwire means "µs became
|
||||
|
|
|
|||
Loading…
Reference in a new issue